This invention relates to medical devices that apply an RF electrical current to tissue of a patient in order to heat the tissue to induce coagulation.
Devices that perform localized heating of tissue may apply an RF electrical current through the tissue by means of electrical contacts. Tissue in the vicinity of an electrical contact is heated through resistance of the tissue to the electrical current. Such tissue heating devices may typically apply current having an intensity and duration that is empirically calculated to heat the tissue to a desired temperature. Nevertheless, the actual extent of heating is unpredictable. Excessive heating of the tissue can cause complete desiccation or "charring" of the tissue that surrounds one or more electrical contacts. A film of charred tissue around an electrical contact can result in a high impedance between the electrical contacts that in turn leads to a cessation of the heating process. Moreover, excessive heating of the tissue can cause an electrical contact to stick to the tissue.